• Corrosion Science and Technology
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• v.16 no.2
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• pp.69-75
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• 2017

Zinc coating on carbon steels give the higher corrosion resistance in chloride containing environments and in carbonated concrete. However, hydrogen evolution accompanies the corrosion of zinc in the initial activity in fresh concrete, which can lead to the formation of a porous structure at the reinforcement -concrete interface, which can potentially reduce the bond-strength of the reinforcement with concrete. The present study examines the mechanism of the corrosion of hot-dip galvanized steel in detail, as in the model pore solutions and real concrete. Calcium ion plays an important role in the corrosion mechanism, as it prevents the formation of passive layers on zinc at an elevated alkalinity. The corrosion rate of galvanized steel decreases in accordance with the exposure time; however, the reason for this is not the zinc transition into passivity, but the consumption of the less corrosion-resistant phases of hot-dip galvanizing in the concrete environment. The results on the electrochemical tests have been confirmed by the bond-strength test for the reinforcement of concrete and by evaluating the porosity of the cement adjacent to the reinforcement.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.37 no.4
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• pp.269-274
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• 2004

Genetic responses of the edible seaweed Porphyra yezoensis tissue to acid shock have been compared using differential display technique. The tissue was challenged in seawater containing $0.05{\%}$ hydrogen chloride (pH 3.0) for 5 min, then rehabilitated in normal seawater for 10 min, 30 min, 60 min and 4 hrs. Total RNA extracted by the LiCl-guanidium method was reverse transcribed and amplified by PCR with arbitrary primers. The amplified fragment responded by the acid shock was selectively isolated from agarose gel and sequenced with DNA auto sequencer. Sequence (1056 bp) of the cDNA contained at least two genes for ASP7K (MW 7418) and ASP5K (MW 5512) proteins.

• Macromolecular Research
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• v.16 no.4
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• pp.373-378
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• 2008

A simple chemical fixation method for the fabrication of layer-by-layer (LbL) polyelectrolyte multilayer (PEM) has been developed to create a large area, highly uniform film for various applications. PEM of weak poly-electrolytes, i.e., polyallylamine hydrogen chloride (PAH) and poly(acrylic acid)(PAA), was assembled on polymer substrates such as poly(methyl methacrylate)(PMMA) and polycarbonate (PC). In the case of a weak polyelectrolyte, the fabricated thin film thickness of the polyelectrolyte multilayers was strongly dependent on the pH of the processing solution, which enabled the film thickness or optical properties to be controlled. On the other hand, the environmental stability for device application was poor. In this study, we utilized the chemical fixation method using glutaraldehyde (GA)-amine reaction in order to stabilize the polyelectrolyte multilayers. By simple treatment of GA on the PEM film, the inherent morphology was fixed and the adhesion and mechanical strength were improved. Both surface tension and FT-IR measurements supported the chemical cross-linking reaction. The surface property of the polyelectrolyte films was altered and converted from hydrophilic to hydrophobic by chemical modification. The possible application to antireflection coating on PMMA and PC was demonstrated.

• Korean Journal of Pharmacognosy
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• v.35 no.1 s.136
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• pp.28-34
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• 2004

DNA damage induced by reactive oxygen species (ROS) seems to play an important role in the induction of mutation and cancer. Hydrogen peroxide $(H_2O_2)$ has been shown to induce a variety of genetic alterations, probably by the generation of hydroxyl radicals via Fenton reaction. In this study, we examined the ability of medicinal herbs in the suppression of $H_2O_2$-induced mutagenesis. Human fibroblast GM00637 cells were treated with $H_2O_2$ in the presence or absence of medicinal herbs, and $H_2O_2$-induced mutant frequency was measured at the hypoxanthine guanine phosphoribosyl transferase (HPRT) locus. Treatment of cells with various doses of $H_2O_2$ caused a significant increase of the HPRT mutant frequency. However, pretreatment of cells with several medicinal herbs reduced $H_2O_2$-induced mutant frequency. The strong antimutagenic effects were observed from the methylene chloride and ethyl acetate fractions of Selaginella tamariscina, Panax ginseng, and Angelica acutiloba; ethyl acetate fractions of Rehmania glutinosa, Leonurus sibiricus, Curcuma zedoaria and Commiphora molmol; butanol fractions of Scutellaria barbata, Tribulus terrestris, Curcuma zedoaria, Cyperus rotundus and Carthamus tinctorius, which were more than 60% inhibition of $H_2O_2$-induced mutant frequency at the HPRT locus.

• Bulletin of the Korean Chemical Society
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• v.12 no.4
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• pp.371-373
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• 1991

The crystal structure of eprazinone dihydrochloride, $C_{24}H_{32}N_2O_2$${\cdot}$2HCl, has been determined from 2102 independent reflections collected on an automated Nonious CAD-4 diffractometer using graphite-monochromated $Mo-K\alpha$ radiation. The crystals are monoclinic, space group P$2_1$/n, with unit cell dimensions a=11.381(2), b=28.318(2), c=7.840(1) $\AA$, $\beta=92.45(2)^{\circ}$, ${\mu}=2.37$ c$m^{-1}$, F(000)=968, and Z=4. Final R value is 0.071 for independent 2102 observed reflections. The molecule assumes an extended conformation. The piperazine ring has a normal chair conformation and the four carbon atom are planar with a maximum displacement of 0.004 $\AA$ for C(18) atom. The two chloride ions are hydrogen bonded to the two piperazine nitrogen atoms [N(14)${\cdot}{\cdot}{\cdot}$Cl(1); 2.986(6) $\AA$ N(17)…Cl(2); 3.084(8) $\AA$].

• Journal of the Korean Society of Propulsion Engineers
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• v.19 no.3
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• pp.96-102
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• 2015

Traditional propellants emit toxic gases such as carbon dioxide and hydrogen chloride during combustion which are harmful to the environment. This study established a synthetic process of a high nitrogen containing derivative of tetrazine, 3,3-Azobis(6-Amino-1,2,4,5-Tetrazine) (DAAT), which can be applied as solid fuels for a solution to environmental concerns. Also, this paper described the detailed process and the analytic results of properties, which were not mentioned in previous reports. The compound was characterized by NMR, IR spectroscopy, and thermal, impact, and friction stability were measured. In addition, the heats of formation (${\Delta}H_f$) and detonation properties (pressure and velocity) of DAAT were calculated using Gaussian 09 and EXPLO5 programs.

• Journal of Soil and Groundwater Environment
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• v.17 no.1
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• pp.22-32
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• 2012

This study suggests a method to grade groundwater quality quantitatively using statistical approaches for evaluating the quality of groundwater in wells included in the Groundwater Quality Monitoring Network (GQMN). The proposed analysis method is applied to GQMN data from 2001 to 2008 for nitrate nitrogen, chloride, trichloroethylene, potential of hydrogen (pH), and electrical conductivity. The analysis results are obtained as groundwater quality grades of the groundwater representing each of the monitoring stations. The degree of groundwater contamination is analysed for water quality parameters, district, and usage. The results show that the degree of groundwater contamination is relatively high by nitrate nitrogen, bacteria and electrical conductivity and at Seoul, Incheon, Gwangju, Gyeonggido and Jeollado. The degree of contamination by nitrate nitrogen and trichloroethylene is especially high when the groundwater is used for agricultural and industrial water, respectively. It is evaluated that potable groudnwater in GQMN is significantly vulnerable to nitrate nitrogen and bacteria contamination.

• Journal of Sensor Science and Technology
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• v.32 no.2
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• pp.82-87
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• 2023

This study proposes a pH-dissolved-oxygen monitoring system using 8-HydroxyPyrene-1,3,6-trisulfonic acid Trisodium Salt (HPTS) and tris(4,7-diphenyl-1,10-phenanthroline)Ruthenium(II) chloride (Ru_dpp). Commercial water-quality sensors are electrochemical devices that require frequent calibration and cleaning, are subject to high maintenance costs, and have difficulties conducting measurements in real-time. The proposed pH-dissolved-oxygen monitoring system selects a thin-film sensing layer to measure the change in fluorescence intensity. This change in fluorescence intensity is based on reactions with hydrogen ions in an aqueous solution at a given pH and specific amount of dissolved oxygen. The change in fluorescence intensity is then measured using light-emitting diodes and photodiodes in response to HPTS and Ru_dpp. This method enables the development of a relatively small, inexpensive, and real-time measureable water-quality measurement system.

• Geomechanics and Engineering
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• v.33 no.2
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• pp.121-131
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• 2023

Clay sedimentation has been widely analyzed for its application in a variety of geotechnical constructions such as mine tailing, artificial islands, dredging, and reclamation. Chemical flocculants such as aluminum sulfate (Al₂(SO₄)₃), ferric chloride (FeCl₃), and ferric sulfate (Fe(SO₄)₃), have been adopted to accelerate the settling behaviors of clays. As an alternative clay flocculant with natural origin, this study investigated the settling of xanthan gum-treated kaolinite suspension in deionized water. The sedimentation of kaolinite in solutions of xanthan gum biopolymer (0%, 0.1%, 0.5%, 1.0%, and 2.0% in a clay mass) was measured until the sediment height was stabilized. Kaolinite was aggregated by xanthan gum via a direct electrical interaction between the negatively charged xanthan gum molecules and positively charged edge surface and via hydrogen bonding with kaolinite particles. The results revealed that the xanthan gum initially bound kaolinite aggregates, thereby forming larger floc sizes. Owing to their greater floc size, the aggregated kaolinite flocs induced by xanthan gum settled faster than the untreated kaolinite. Additionally, X-ray computed tomography images collected at various depths from the bottom demonstrated that the xanthan gum-induced aggregation resulted in denser sediment deposition. The findings of this study could inspire further efforts to accelerate the settling of kaolinite clays by adding xanthan gum.

• Journal of the Korean institute of surface engineering
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• v.57 no.3
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• pp.201-207
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• 2024

This study compared the chemical resistance properties according to various sealing treatment methods for the anode film formed during the anodization process of Al6061 alloy. Al6061 aluminum was used in four different sealing treatment methods: boiling water sealing, lithium sealing, nickel sealing, and pressurized sealing, and each sample was evaluated for corrosion resistance through a 5% HCl bubble test and the microstructure was observed through a scanning electron microscope(SEM). According to the results, corrosion resistance increased as time and temperature increased in all sealing treatment methods. Relatively, corrosion resistance was high in the order of boiling water sealing, lithium sealing, nickel sealing, and pressure sealing, and the best corrosion resistance was found in pressure sealing. These research results can be helpful in selecting a process necessary to improve the efficiency and performance of anodizing process in the industrial field using aluminum alloys.